Technical Field
The present disclosure relates to the field of optical technologies, and in particular, to a projection system.
Description of the Related Art
At present, digital light processing (DLP) projection technology based on a digital micromirror device (DMD) has been more and more widely used. The most widely used DLP projection systems are single-chip DMD projection systems and three-chip DMD projection systems.
As shown in FIG. 1, a single-chip DMD projection system includes a light source 100, a collecting lens 101, a rotating color wheel 102, a square rod 103, a light relay system 104, a DMD chip 105, a TIR prism 106, and a projection lens 107, where the light source 100 is a semiconductor laser or a light emitting diode. Excitation light emitted by the light source 100 passes through the collecting lens 101 and then is focused onto the rotating color wheel 102. The rotating color wheel 102 has three kinds of fluorescent powder of red R, green G, and blue B and different kinds of fluorescent powders are located in different areas of the rotating color wheel 102 as shown in FIG. 2. Light of three primary colors of red R, green G, and blue B having a time sequence can be generated after the excitation light is incident on different areas of the rotating color wheel 102. The light of the three primary colors sequentially passes through the square rod 103 and the light relay system 104, and then is incident on the TIR prism 106 and reflected by the TIR prism 106 to the DMD chip 105 for modulation, by which an image is formed and then outputted from the projection lens 107.
In the aforementioned single-chip DMD projection system, the light of the three primary colors of red R, green G, and blue B is sequentially incident on the DMD 105 in a time sequence for modulation, and then monochrome images obtained after modulation are synthesized into a color image through an integral effect of human eyes. However, in a three-chip DMD projection system, each DMD modulates one kind of primary light, for example, the first DMD modulates red light R, the second DMD modulates green light G, and the third DMD modulates blue light B, and then monochrome images obtained after modulation by the three DMDs are spatially superimposed for synthesizing a color image. That is to say, in existing DLP projection systems, regardless of single-chip DMD projection systems or three-chip DMD projection systems, color images are synthesized based on the principle of three primary colors.
Although the color gamut of the aforementioned color image basically meets the REC.709 standard, and the color gamut of the color image LP covers a large part of the REC.709 color gamut as shown in FIG. 3, the color gamut does not completely cover the REC.709 color gamut, that is, some of the existing DLP projection systems still fail to meet the REC.709 standard, let alone the DCI standard.